Folk music of the Pete Seeger school was about singing along and the community that built: we shall overcome, not I. The underground rock of the late '90s created such communities by looking inward, only to find common wounds and fears. Few bands from that era are as deeply strange or as emotionally resonant as Neutral Milk Hotel, whose 1998 opus "In the Aeroplane Over the Sea" is, among many things, a nasally sung concept record that ties together themes of Anne Frank, sexual violence and fractured families. Many consider it a singular classic: they are correct. It also makes for an excellent sing-a-long.

So what would become of these songs at the Crystal Ballroom on Sunday night, some 16 years later? Woken from a long slumber, would the songs age as if they'd been played all this time instead?

Neutral Milk Hotel frontman Jeff Mangum vanished for a long time after the original "Aeroplane" tour, appearing on stage with colleagues here and there and finally touring solo after a surprise show in Brooklyn in 2010. That was an extensive warm-up for the band's full-scale return, which began last year. I hadn't seen any of those shows, which were received by friends and fans with seemingly religious fervor. So my expectations were high on Sunday, as was the regrettable alcohol intake of some in the audience who arrived late and pushed their way forward, a breach of concert etiquette usually reserved for rowdier bands.

But Neutral Milk Hotel was rowdy enough: they played many of their songs, including "Holland, 1945" and "King of Carrot Flowers Pts. 2 & 3," at a careening pace, sounding at times like a punk band with a horn section, though not like Reel Big Fish. On record, Mangum is a calming presence, always central and clear: it's easy not to notice how quickly the band plays behind him on those songs, though they made themselves known on Sunday. It was like seeing an old classmate at a high school reunion after years of examining yearbooks and not recognizing him at first: jarring, then familiar.

The ensemble was a stirringly woozy presence on "Fool," taking the stage as Mangum finished up set opener "Two-Headed Boy" in a neat recreation of an "Aeroplane" transition. The Crystal's sound was messier than usual, though whether that was a venue issue or a band with a menagerie of instruments playing too hot was hard to say: more clarity would've improved their performance, but not the miraculous sight of the band on stage, rocking like teenagers.

"In the Aeroplane Over the Sea," at its heart, was a lament for lost youth. Neutral Motel Hotel's return is a realization that the fight's not over yet. (Fans haven't given up: the band has sold out a second show on Monday.) Mangum's knife of a voice found its edge as the show went on, though the passing decade-plus has shifted his tone and left certain high notes out of reach. He was at his most ferocious on "Oh Comely," a song he performed mostly by himself; he seemed most joyful swinging his guitar with the group during instrumental breaks. The set's second half was slower, prettier: the band played a medium-sized encore, wrapping with the gentle "Engine" and ushering the crowd into the night. It wasn't religion, but as rock 'n' roll, it was enough.